Dual absolute encoder

ABSTRACT

An exemplary encoder assembly includes a substrate, a first encoder, and a second encoder. The substrate has two or more position sensors, each position sensor being configured for detecting a rotary position of a shaft or other rotating element of a machine. The first encoder includes at least one first position sensor of the two or more position sensors. The at least one first position sensor is disposed on the substrate for off-axis alignment with the shaft or other rotating element of the machine. The second encoder includes a second position sensor of the two or more position sensors, the second position sensor being disposed on the substrate for on-axis or off-axis alignment with the shaft or other rotating element of the machine. Each position sensor is configured to detect different or common signal types, and a signal type of the second position sensor excludes optical signals.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.17/338,799 filed on Jun. 4, 2021, which is a continuation ofInternational Application No. PCT/US2018/064182 filed Dec. 6, 2018.

FIELD OF THE INVENTION

The present disclosure relates generally to an absolute encoder, andparticularly to a dual magnetic absolute encoder.

BACKGROUND OF THE INVENTION

Encoders have a wide variety of uses in products which require speedand/or position control for motors. An encoder is a type of transducerthat converts linear or angular mechanical motion into an electricalsignal. A linear encoder can be used to measure and indicate theposition of a movable member. A rotary encoder is used to measure theangular position of a rotating member of a device or system. In roboticsystems, for example, a rotary encoder can be used to detect theposition of a rotating shaft, which can be connected to move a roboticarm. Absolute encoders are popular in these types of systems because ofa capability to determine an actual or absolute position. The absoluteencoder can at all times provide a reliable indication of a trueposition of the motor shaft of a component to which it is attached.

An absolute encoder uses a sequence of positional codes stored in binaryform on a code disk and a single or plurality of sensors that read thepositional codes. A linear encoder uses an elongated component havinglengthwise parallel code tracks. A rotary encoder uses code disks havingone or more concentric code tracks. Sensors are used to read the codes.The sensors can use any of optical, magnetic, inductive, capacitive ordirect contact as a manner of reading the codes. The type of sensorsused can depend on the application and/or environment in which thesystem will operate.

SUMMARY OF THE INVENTION

An exemplary embodiment of the present disclosure is directed to anencoder assembly, comprising: a substrate having two or more positionsensors, each position sensor being configured for detecting a rotaryposition of a shaft or other rotating element of a machine; a firstencoder including at least one first position sensor of the two or moreposition sensors, the at least one first position sensor being disposedon the substrate for off-axis alignment with the shaft or other rotatingelement of the machine; and a second encoder including a second positionsensor of the two or more position sensors, the second position sensorbeing disposed on the substrate for on-axis or off-axis alignment withthe shaft or other rotating element of the machine, wherein eachposition sensor is configured to detect different or common signaltypes, and a signal type of the second position sensor excludes opticalsignals.

An exemplary encoder assembly comprising: a code disk configured forattachment to the shaft or other rotating element of the machine,wherein the at least one first position sensor and the second positionsensor are disposed on the substrate to be planar with an axial surfaceof the code disk, and wherein the code disk, the at least one firstposition sensor, and the second position sensor form dual multi-turnabsolute encoders.

An exemplary encoder assembly comprising: a code disk configured forattachment to the shaft or other rotating element of the machine,wherein the substrate includes a first portion configured to be parallelwith an axial surface of the code disk and a second portion configuredto be parallel with a radial surface of the code disk, and wherein theat least one first position sensor is disposed on the second portion ofthe substrate and the second position sensor is disposed on the firstportion of the substrate.

An exemplary encoder assembly comprising: a code disk including a firstcode disk configured to be disposed within a hollow volume of the shaftor other rotating element of the machine, and a second code diskconfigured for attachment to a surface of the shaft or other rotatingelement of the machine, wherein the at least one first position sensoris disposed on the substrate for detecting a signal from the second codedisk, and the second position sensor is disposed on the substrate foron-axis alignment with the shaft or other rotating element of themachine to detect a signal from the first code disk, and wherein the atleast one first position sensor is configured to detect a signal from anaxial or radial surface of the second code disk.

An exemplary encoder assembly comprising: a code disk including a firstcode disk configured to be disposed within a hollow volume of the shaftor other rotating element of the machine, and a second code diskconfigured for attachment to a surface of the shaft or other rotatingelement of the machine, the substrate includes a first portionconfigured to be parallel with an axial surface of the first code diskand a second portion configured to be parallel with a radial surface ofthe second code disk, and the at least one first position sensor isdisposed on the second portion of the substrate for detecting a signalfrom the radial surface of the second code disk and the second positionsensor is disposed on the first portion of the substrate for detecting asignal from an axial surface of the first code disk.

An exemplary encoder assembly comprising: a code disk including a firstcode disk and a second code disk configured for attachment to a surfaceof the shaft or other rotating element of the machine, wherein thesubstrate includes a first portion configured to be parallel with aradial surface of the first code disk, a second portion configured to beparallel with a radial surface of the second code disk, and a thirdportion extending between the first and second portions, wherein the atleast one first position sensor is disposed on the first portion of thesubstrate for detecting a signal from the radial surface of the firstcode disk, the second position sensor is disposed on the second portionof the substrate for detecting a signal from the radial surface of thesecond code disk, and circuitry is mounted to the third portion of thesubstrate, and wherein the first and second portions of the substrateare parallel with an axis of the shaft and orthogonal to the thirdportion.

An exemplary encoder assembly wherein the at least one first positionsensor and the second position sensor are embedded within layers of thesubstrate.

An exemplary encoder assembly wherein the two or more position sensorsare connected to a common bus or separate data lines, and wherein thecommon bus and the separate data lines are configured to communicateposition data and/or clock signals and/or other data.

An exemplary encoder assembly wherein the first encoder is a magneticencoder, a capacitive encoder, an inductive encoder, or an opticalencoder, and the second encoder, disposed on the substrate for on-axisor off-axis alignment with the shaft or other rotating element of themachine, is a magnetic encoder, a capacitive encoder, or an inductiveencoder.

An exemplary encoder assembly connected in combination with acontroller, wherein: the controller is configured to detect a faultbased on rotary positions detected by the two or more position sensors,and the controller is configured to compare the rotary positionsdetected by the two or more position sensors and generate a fault signalwhen the compared rotary positions are outside a predeterminedtolerance.

An exemplary encoder assembly wherein the substrate includes a powercircuit connected to the first and second encoders, the power circuitbeing configured to provide circuit protection at least against powersurges.

Another exemplary embodiment of the present disclosure is directed to anactuator assembly, comprising: a motor having a motor shaft and anoutput shaft coaxial with the motor shaft; and an encoder assemblyincluding: a first encoder configured in off-axis alignment with themotor shaft; a second encoder configured in on-axis or off-axisalignment with the motor shaft; and a common substrate on which positionsensors of the first encoder and the second encoder are mounted, whereinthe common substrate is configured to communicate position data from theposition sensors, and wherein each position sensor is configured todetect different or common signal types, and a signal type of the secondencoder excludes optical signals.

An exemplary actuator assembly wherein the second encoder, if in on-axisalignment with the motor shaft, includes a first code disk disposed in ahollow volume of the output shaft and the first encoder includes asecond code disk attached to a surface of the motor shaft.

An exemplary actuator assembly wherein the second encoder, if inoff-axis alignment with the motor shaft, includes a second positionsensor configured to detect signals from an axial surface of the firstcode disk.

An exemplary actuator assembly wherein the common substrate includes afirst portion on which a second position sensor of the second encoder ismounted for detecting signals from an axial surface of the first codedisk, and a second portion on which a first position sensor of the firstencoder is mounted for detecting signals from a radial surface of thesecond code disk, and wherein the second portion of the common substrateis perpendicular to the first portion of the common substrate.

An exemplary actuator assembly wherein the encoder assembly includes acontroller configured to control the operation of the actuator assemblybased on the position data detected by the position sensors, wherein thecontroller is mounted on the common substrate.

An exemplary actuator assembly wherein the controller is configured todetect a fault based on rotary positions of the motor shaft detected bythe second encoder and rotary positions of the output shaft detected bythe first encoder, and wherein the controller is configured to comparethe rotary positions of the motor shaft and the output shaft andgenerate a fault signal when the compared rotary positions are outside apredetermined tolerance.

An exemplary actuator assembly wherein the first encoder is a magneticencoder, a capacitive encoder, an inductive encoder, or an opticalencoder and the second encoder, in on-axis or off-axis alignment withthe motor shaft, is a magnetic encoder, a capacitive encoder, or aninductive encoder.

An exemplary actuator assembly wherein the first encoder and the secondencoder are absolute encoders.

An exemplary actuator assembly wherein each position sensor is disposedon the common substrate to detect a signal from an axial surface of arespective code disk.

An exemplary actuator assembly wherein: the first encoder including afirst position sensor disposed on the common substrate to detect asignal from a radial surface of a first code disk; and the secondencoder including a second position sensor disposed on the commonsubstrate to detect a signal from an axial surface of a second codedisk, wherein the substrate includes a first portion on which the secondposition sensor is mounted for detecting signals from the axial surfaceof the second code disk, and a second portion on which the firstposition sensor is mounted for detecting signals from the radial surfaceof the first code disk.

An exemplary actuator assembly wherein: the first encoder including afirst position sensor disposed on the common substrate to detect asignal from a radial surface of a first code disk, the second encoderincluding a second position sensor disposed on the common substrate todetect a signal from a radial surface of a second code disk, wherein thecommon substrate includes a first portion on which the first positionsensor is mounted for detecting signals from the radial surface of thefirst code disk, and a second portion on which the second positionsensor is mounted for detecting signals from the radial surface of thesecond code disk, and a third portion extending between the first andsecond portions on which encoder circuitry is mounted, wherein the firstand second portions of the substrate are parallel with an axis of themotor shaft and orthogonal to the third portion.

An exemplary actuator assembly wherein the position sensors areconnected to a common bus or separate data lines, and wherein the commonbus and separate data lines are configured to communicate position dataand/or clock signals and/or other data.

An exemplary actuator assembly connected in combination with thecontroller, wherein the controller is configured to detect a fault basedon rotary positions detected by two or more position sensors, andwherein the controller is configured to compare the rotary positionsdetected by the two or more position sensors and generate a fault signalwhen the compared rotary positions are outside a predeterminedtolerance.

An exemplary actuator assembly wherein the common substrate includes apower circuit connected to the plurality of encoders, the power circuitbeing configured to provide circuit protection.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The scope of the present disclosure is best understood from thefollowing detailed description of exemplary embodiments when read inconjunction with the accompanying drawings, wherein:

FIG. 1 illustrates an actuator assembly in accordance with an exemplaryembodiment of the present disclosure.

FIGS. 2 a and 2 b illustrate an exemplary optical or capacitive encoderassembly according to an exemplary embodiment of the present disclosure.

FIGS. 3 a-3 c illustrate exemplary encoder assemblies according to anexemplary embodiment of the present disclosure.

FIGS. 4 a and 4 b illustrate an exemplary controller circuit inaccordance with an exemplary embodiment of the present disclosure.

FIGS. 4 c and 4 d illustrate wiring schemes of the position sensor andsubstrate assembly in accordance with an exemplary embodiment.

FIGS. 5 a-5 c illustrate types of magnets for an encoder assembly inaccordance with an exemplary embodiment of the present disclosure.

FIGS. 6 a-6 g illustrate various mounting arrangements of the positiondetection sensors in accordance with an exemplary embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary dual absolute encoder can be configured to include twoencoders each having rotary position sensors disposed on a commonsubstrate. One encoder can include a position sensor arranged (e.g.,disposed, positioned, mounted) on the substrate to be on center oron-axis with respect to a motor shaft when the substrate is mounted tothe motor. A second encoder can include a position sensor arranged onthe substrate to be off-center or off-axis with respect to the axis ofthe motor shaft. The dual encoder arrangement can provide improvedresolution and provide redundancy when determining the position orrotation of the motor shaft.

FIG. 1 illustrates an actuator assembly in accordance with an exemplaryembodiment of the present disclosure. The actuator assembly 100 caninclude an actuator housing 102 that has a seal 106 that the actuatoroutput flange 104 rotates within. This actuator output flange 104includes features (e.g., holes) 108 for mounting the output of theactuator assembly 100 to an external load (not shown). A hollow motorshaft 110 is coaxial with an actuator output shaft 112. The hollow motorshaft 110 has a front-end 114 and a rear-end 116 extends along thecenter axis (x) of the housing 102. The front-end 114 is coupled to thegear input 118 (e.g., inner diameter of an elliptical wave generator)that creates the reduction between two internal splines (not shown)connecting the housing 102 and the motor assembly. The actuator outputflange 104 is supported by a bearing 120. The actuator assembly 100 alsoincludes a stator 122 that is fixed to an interior surface of thehousing 102 and is spaced from the motor shaft 110 via a gap 124 thatsurrounds the motor shaft 110.

An encoder assembly 126 is configured for detecting position androtation at the rear-end 116 of the motor shaft 110, which is coaxialwith an end of the actuator output shaft 112. The encoder assembly 126can be configured as an absolute rotary encoder that is at leastpartially mounted or attached to the stator 122 and/or housing 102 ofthe actuator assembly 100 via a mounting bracket or spacer 128. Themounting bracket 128 can be securely attached to the actuator assembly100 via screws or bolts 130 or other suitable holding mechanisms asdesired.

As shown in FIG. 1 , the encoder assembly 126 includes a code disk 132Afor generating the position signal associated with the motor shaft 110,and a code disk 132B for generating the position signal associated withthe actuator output shaft 112 that may include the output of a gearwhere the gear input 118 is attached to the motor shaft 110. Alsoincluded is a substrate 134 that includes at least circuits formonitoring the position of the motor shaft 110 and the actuator outputshaft 112. The substrate 134 can be implemented as a printed circuitboard, a planar 3D printed material, a flexible circuit board, or anyother known component configured to mechanically support andelectrically connect electrical components of a single modular board asdesired. The substrate 134 can have a multilayer construction in whichthe wiring portion and component and circuit layout meet specifiedperformance power, and thermal characteristics. The substrate 134 caninclude a plurality of position detection sensors 136A, 136B fordetecting a rotary position of coaxial shafts or other rotating elementsand connected to a common bus for communicating data with a controller.The position detection sensors 136A, 136B can be mounted on a surfaceand/or embedded within interior layers of the substrate 134 as desired.The position detection sensors 136A, 136B can be electrically connectedto each other and/or to other components and circuits on the substratethrough the use of conductive tracks, pads, vias, and other known meansof establishing electrical connections as desired on a substrate. Theposition detection sensor 136A is arranged on the substrate 134 todetect signals from the code disk 132A, which in combination theposition detection sensor 136A and the code disk 132A form an encoder.The position detection sensor 136B is arranged on the substrate 134 todetect signals from the code disk 132B. The combination of the positiondetection sensor 136B and the code disk 132B also forms an encoder.

The position detection sensors 136A, 136B can be non-contacting andconfigured to detect the position of the motor shaft 110 and/or theactuator output shaft 112 through magnetic or inductive signals emittedfrom associated code disks as shown in FIG. 1 . According to otherexemplary embodiments disclosed herein, the position detection sensorcan be configured to use optical or capacitive signaling means or a mixof both. These alternate embodiments are disclosed in further detail inrelation to FIGS. 2 a and 2 b .

According to an exemplary embodiment of the present disclosure, the codedisk 132A is configured with a plurality of alternating magnetic poles(N, S) provided on an axial (FIG. 1 .) or radial (FIG. 3 a ) surfacerelative to the axis of the motor shaft 110. The position detectionsensors 136A, 136B can be implemented as Hall-effect elements formagnetically detecting the position of a rotation shaft via the codedisks 132A, 132B respectively. The position detection sensors 136A, 136Bin combination with the code disks 132A, 132B can be configured assingle-turn absolute encoders, which measure displacement or rotation ofthe shaft across a 360° range from a specified position at start-up. Inthis configuration, the output of the position detection sensor 136A,136B is repeated for each revolution or rotation cycle of the motorshaft 110. The use of absolute encoders in this configuration providesredundancy for improved safety generally in controlling the operation ofthe motor and more particularly, in determining the position of themotor shaft 110. In accordance with another exemplary embodiment of thepresent disclosure, one or more encoders of the encoder assembly 126 canbe configured as multiple-turn (or multi-turn) absolute encoders. In themulti-turn absolute encoder configuration, the encoder assembly 126 caninclude multiple code disks and a battery (not shown) and/or a counter(not shown) for maintaining position information at power shutdown. Asalready discussed, the actuator output shaft 112 can include gearing118. As a result, the motor shaft 110 may rotate a number of revolutionsaccording to a gear ratio to accumulate one revolution of the actuatoroutput shaft 112. Because the absolute starting position of each sensorcan be determined at startup, no battery backup is required for storingthe absolute position data within one revolution of the actuator outputshaft 112.

FIGS. 2 a and 2 b illustrate an exemplary optical or capacitive encoderassembly according to an exemplary embodiment of the present disclosure.As shown in FIGS. 2 a and 2 b , the position detection sensors 236A,236B can be implemented as optical or capacitive photo electric sensorsand are used in combination with code disks 232A, 232B, respectively.The code disks 232A, 232B can have a plurality of opaque or transparentareas configured for passing light through its surfaces. A light source(not shown) can be positioned adjacent a respective code disk 232A, 232Band on a side opposite the position detection sensors 236A, 236B inorder to illuminate the code disk 232A, 232B. As the code disk 232A,232B rotates the position detection sensors 236A, 236B detect themodulated light as it passes through the transparent and/or opaqueareas. A controller is configured to access memory to determine apredetermined position or rotation of the shaft associated with thedetected modulated signals. The exemplary encoder assembly 226 as shownin FIG. 2 a can also include any number of optical elements for focusingthe light onto the position detection sensors 236A, 236B. The opticalelements can include light collimating light emitting diodes, mirrors,prisms, lenses, fiber optics, laser diodes, optical slits, diffractiongratings, or any other suitable light directing element or mechanism asdesired. As shown in FIG. 2 a , the optical or capacitive encoderassembly can be configured such that each sensor is mounted to a singlesubstrate 234, which is formed as a ring, on either a surface facing therear-end 116 or surface facing the front-end 114 of the substrate asdesired. FIG. 2 b illustrates an exemplary embodiment in which a singleposition detection sensor 236A mounted to a single substrate 234 is anoptical sensor used for detecting the light passing through each codedisk 232A.

According to another exemplary embodiment of the disclosure, theposition detection sensors 236A, 236B can be used in combination withcode disks 232A, 232B configured to have a predetermined sinusoidalpattern etched onto the respective surfaces. In accordance with thisexemplary embodiment, the encoder assembly 226 includes a transmitter(not shown) that generates a high frequency signal for injection intothe motor shaft 110. As the code disks 232A, 232B rotate with the motorshaft 110 the sinusoidal pattern modulates the high-frequency signal ofthe transmitter. The position detection sensors 236A, 236B can beconfigured as capacitive sensors, which detect the modulated signal fromthe code disks 232A, 232B and provide the signal to thedriver/controller. The driver/controller translates the modulated signalreceived from the position detection sensors 236A, 236B into rotarymotion, and uses the rotary motion value to determine the position ofthe motor shaft. As shown FIG. 2 b , the encoder assembly 226 caninclude a combination of optical or capacitive position detectionsensors 236A in off-axis positions relative to the motor shaft 110 witha magnetic position detection sensor 236B in an on-axis position.

FIGS. 3 a-3 c illustrate an encoder assembly according to an exemplaryembodiment of the present disclosure. As shown in FIG. 3 a , the encoderassembly 326 can be configured to have two mated, ring-shaped substratesserving as the code disks 332A, 332B. The code disk 332B can be attachedto the motor shaft 110 so that it can synchronously rotate with themotor shaft 110 during operation. The code disk 332A is mounted to theactuator output shaft 112 of the actuator assembly 100. The code disk332B is configured to include position detection sensor 336B and othercomponents including, for example, a power circuit (not shown) embeddedwithin its internal layer structure. During operation of the motorassembly, the code disk 332B rotates with the motor shaft 110 and theposition detection sensor 336B detects changes in inductive couplinggenerated as the code disk 332B rotates with the motor shaft 110. Themagnetic signals detected by the position detection sensor 336B arecompared with predetermined magnetic signal measurements to determine aposition of the motor shaft 110. As shown in FIG. 3 a , the substrate334 can include a first portion 334A and a second portion 334B. Theposition detection sensor 336A can be mounted on the first substrateportion 334A to be in off-axis alignment with the motor shaft 110 todetect signals from the code disk 332A mounted to the output shaft 112.The position detection sensor 336B can be mounted on the secondsubstrate portion 334B to be in off-axis alignment with the motor shaft110 to detect signals from code disk 332B mounted to the motor shaft110. The position detection sensor 336B is arranged to detect signalsfrom a radial surface of the code disk 332B. As shown in FIG. 3 b , thissame design can be implemented for the actuator output shaft 112 and itsring shaped substrate 334, where position detection sensor 336B ismounted on the opposite side of the substrate 334 from the positiondetection sensor 336A with redundancy. FIG. 3 c illustrates the encoderassembly of FIG. 3 b without redundancy. According to an exemplaryembodiment, the encoder assembly 326 of FIGS. 3 b and 3 c can beconfigured to use magnetic or inductive position detection.

According to an exemplary embodiment of the present disclosure, theencoder assembly 326 can be configured to include any combination ofmagnetic, optical, inductive, and/or capacitive encoders as disclosedherein. For example, the encoder assembly 326 can include an encoderhaving a magnetic code disk 332B disposed in the hollow volume on a sidefacing the rear-end 116 of the motor shaft 110. Another exemplaryencoder can be configured with an optical code disk 332A attached to theactuator output shaft 112 so that it rotates during operation of theactuator assembly. Position detection sensors 336A, 336B can be alignedin off-axis positions on the substrate 334 relative to the axis (X) ofthe motor shaft 110. The position detection sensor 336A is configured todetect the light reflected from the optical code disk 332A, and theposition detection sensor 336B is configured to detect the signalsemitted from the magnetic code disk 332B.

FIGS. 4 a-4 c illustrate an exemplary controller circuit in accordancewith an exemplary embodiment of the present disclosure. The controller450 can be configured as a servo drive that includes a hardware device,such as a processor, a field programmable gate array (FPGA) or anapplication-specific integrated circuit (ASIC). Each of these devicescan be specially programmed with software or programming code to performoperations to process, analyze, and/or manipulate driving and/orcontrolling the actuator assembly 100 and/or the data detected by theposition detection sensors 436A, 436B and/or other components orcircuits of the actuator assembly 100. The controller 450 can includecomponents and circuitry that can be integrated directly onto thesubstrate 434 as well as the position sensors 436A, 436B that detectrotation of the actuator output shaft 112 and motor shaft 110respectively. The circuits can include, for example, a power circuit402, a fault detection circuit 404, and a driver/controller 450, amongothers. As shown in FIG. 4 a , the circuits can be mounted on one ormore sides or surfaces of the substrate. For example, the power circuit402, fault detection circuit 404, and driver/controller 450 can bemounted on a side A of the substrate 434 and the position detectionsensors 436A, 436B can be mounted on a side B of the substrate 434. Theposition detection sensors 436A, 436B are configured to share a powersignal output from the power circuit 402. FIG. 4 b illustrates anembodiment in which the position detection sensors 436A, 436B areembedded within the substrate 434. It should be understood that any ofthe other components and/or circuits can be embedded within thesubstrate in combination with or in place of the position detectionsensors 436A, 436B. According to an exemplary embodiment, the controller450 can be mounted in any suitable arrangement on the substrate 434 suchthat the various components and circuitry can be mounted to any side Aor B of the substrate or embedded within the substrate in anycombination as desired.

In an alternative embodiment, the controller 450 can be mounted on aseparate substrate within the motor assembly or external to the housing102 of the actuator assembly. The controller 450 can be configured todetermine whether a fault based on rotary positions of the shaftsdetected by at least two of the plurality of position detection sensors436A, 436B. For example, the controller 450 can be configured to comparethe rotary positions of the shaft detected by at least two positiondetectors 436A, 436B and generate a fault signal when the comparedrotary positions are determined to be outside a predetermined tolerance.For example, if a 15 bit (32768 counts per revolution) position detectoris monitoring the motor shaft 110 position, and a 14 bit (16384 countsper revolution) position detector is monitoring the actuator outputshaft 112 position with a 100:1 reduction ratio, and the motor rotates50.75 revolutions, the motor shaft position detector will output the0.75 position of 1 revolution as 24756 counts while the actuator outputwill count 50 revolutions and 0.75 revolutions with its 100:1 reductionas 8192+123 or 8315 counts. The conversion of 1 motor shaft revolutionor 32768 counts equating to 164 actuator position detector counts wouldbe used by the controller to set a fault if the motor position within1000 counts does not correlate to an actuator position within 5 countsdepending on the accuracy and repeatability of the position detectorintegrated since the motor shaft to actuator output position detectionis 200 in this example.

FIGS. 4 c and 4 d illustrate a wiring scheme of the position sensor andsubstrate assembly in accordance with an exemplary embodiment. Accordingto one embodiment an encoder assembly can be configured with multipleposition sensors where each position sensor includes separate data andclock lines or signals. For example, the position detection sensors436A, 436B, 436C can be configured to have data lines 408 and a clocklines 410 connected to a driver/controller 450 and a shared power andground 412 from the power circuit 402. The exemplary embodiment shown inFIG. 4 c differs from and provides advantages over the previousembodiment because it provides an exemplary illustration for connectingthe position detection sensors 436A, 436B, 436C in a daisy chainarrangement such that the sensors share a common data bus. As a resultof this arrangement, the total number of lines necessary for wiring theposition detection sensors 436A, 436B, 436C of the encoder assembly canbe significantly reduced, e.g., the exemplary technique of the presentdisclosure eliminates eight redundant data communication wires (Data+,Data−, Clock+, Clock− for 2 sensors). The exemplary encoder assembly 126of the present disclosure is configured to provide position data orother motor assembly data as desired on the common data bus 414 as amulti-bit word. The encoder assembly can be configured to communicatethe data via a parallel or serial interface. Serial data can be outputaccording to a synchronous serial interface (SSI) protocol or abidirectional/serial/synchronous (BiSS) interface protocol. As shown inFIG. 4 d , the position detection sensors Position Sensors 436A and 436Bare connected according to a differential line transmitter and receiver.For each sensor 436A and 436B, two lines are for the differential datareceive (SLO+and SLO−). Two lines are for differential clock and datatransmit signal (MA+and MA−). The position sensors are connected in amaster (MA)/slave (SLO) arrangement. The arrangement can be scaled toinclude any number of sensors as desired.

FIGS. 5 a-5 c illustrate types of magnets for an encoder assembly inaccordance with an exemplary embodiment of the present disclosure.

As shown in FIG. 5 a , the code disk 532 is representative of the codedisks 132A, 332A, and 332B discussed relative to FIGS. 1 and 3 a-3 c,where applicable. The code disk 532 can be configured as a multi-polemagnet that can be coaxially secured to one or more motor shafts 110 orother rotating elements for which rotation is to be detected. The codedisk 532 in combination with the position detection sensor 136A providesfor off-axis rotation detection relative to the actuator output shaft ormotor shaft 110 as shown in FIG. 1 . The code disk 532 can have a ringor circumferential shape and be configured to include a plurality ofalternating N and S pole pairs 525. The pole pairs N and S can bearranged on an axial surface 515 of the code disk 532 relative to theaxis of the motor shaft 110. According to an exemplary embodiment of thepresent disclosure, the code disk 532 can have any of 16, 32, and 64pole pairs or any other suitable number of poles as desired. The axialsurface 515 of the code disk 532 can include one or more tracks 520,where each track 520 includes a plurality of N and S magnetic poles 525arranged in an alternating pattern along the circumference. For eachtrack 520, the plurality of N and S poles 525 can be spaced atequidistant or equiangular positions around the circumference of thecode disks 532. FIG. 5 a , illustrates a code disk 532 comprised of two(2) tracks 520A, 520B and having a resolution of up to 18 bits (i.e.,262144 counts). For an optical encoder assembly, the transparent oropaque areas are used in place of the N and S pole pairs of the magneticcode disk. It should be understood, however, that the code disks 532 canhave any number of suitable tracks according to the desired resolutionof the position to be detected.

As shown in FIG. 5 b , the code disk 532 can be arranged such that the Nand S pole pairs are formed on a radial surface 510 or outer edge.

As shown in FIG. 5 c , the encoder assembly 126 can include a two (2)pole magnet 535 that is configured to be attached to or disposed withinthe hollow volume of the actuator output shaft 112 for which rotation isto be detected. According to another exemplary embodiment, the two polemagnet 535 can be disposed inside the hollow inner volume of the motorshaft 110 nearest the rear-end 116. The magnet 535 in combination withthe position detection sensor 536 provides for on-axis detectionrelative to the actuator output shaft 112.

FIGS. 6 a-6 g illustrate various mounting arrangements of the positiondetection sensors in accordance with an exemplary embodiment of thepresent disclosure.

As shown in FIG. 6 a , encoder assembly 126 can include a positiondetection sensor 636B disposed on the substrate 634 so that when thesubstrate 634 is mounted on the actuator assembly, the positiondetection sensor 636B is in an on-axis position relative to a code disk632B mounted within the hollow inner volume of the motor shaft 110 orother rotating element for which the position is to be detected. In theon-axis position, the position detection sensor 636B is positioned tosense the poles of the code disk 632B, which is mounted within thehollow volume of the motor shaft 110 nearest the rear-end 116 or on therear-end of the actuator output shaft 112 as shown in FIG. 1 . A codedisk 632A can be mounted to the motor shaft 110, and a positiondetection sensor 636A can be mounted to the substrate 634 in an off-axisposition relative to the motor shaft 110 to detect signals from the codedisk 632A. This arrangement and orientation of the position detectionsensors provides redundancy and improved accuracy over known encoderassembly designs.

As shown in FIG. 6 b , the encoder assembly 126 can include a positiondetection sensor 636B disposed in an on-axis position on the substrate634 relative to the motor shaft 110 as in FIG. 6 a , and also includeone or more position detection sensors 636A disposed in off-axispositions, on the substrate 634 relative to the motor shaft 110. Asalready discussed, in the off-axis position the position detectionsensor 636A is positioned to sense the N and S poles 525 of the codedisk 632A. In an arrangement where at least two position detectionsensors 636A are used, the sensors 636A can be disposed in positionsoffset by an angle of 90° , 180° or any other suitable angle as desired.The position detection sensors 636A, 636B are located on the samesubstrate surface and are therefore, mounted at the same axial positionwith the position detection sensor 636B being on center.

As shown in FIG. 6 c , the encoder assembly 126 can include one or moreposition detection sensors 636A disposed in respective off-axispositions on the substrate 634 relative to the motor shaft 110.Increasing the number of position detection sensors 636A leads toredundancy or better accuracy. According to this embodiment no on-axisposition detection sensors 636B are used for detecting the position ofthe motor shaft 110.

As shown in FIG. 6 d , the encoder assembly 126 can include one or moreposition detection sensors 636B disposed radially relative to the motorshaft 110 and mounted on a first portion 634A of the substrate 634, anda second portion 634B of the substrate 634 extends in a planeperpendicular to the first substrate portion 634A. The first substrateportion 634A is arranged to be adjacent to an axial surface of a codedisk 632B, and the second substrate portion 634B is arranged to beadjacent to a radial surface of the code disk 632B. A position detectionsensor 636C can be mounted to a surface of the perpendicular secondsubstrate portion 634B. The position detection sensor 636C is alignedwith a code disk 632C having pairs of N and S poles 525 arranged on aradial surface 610 or outer edge. The first substrate portion 634A canbe mounted to the stator assembly 122 (FIG. 1 ) and thus thereforestationary during operation. The code disk 632B is mounted to theactuator output shaft 112.

FIGS. 6 e and 6 f illustrate an exemplary encoder assembly in which thesubstrate 634 can be mounted to a stator assembly 122 as shown in FIG. 1. The single substrate 634 is formed to have a central hole or aperture635 that allows complete passage of the actuator output shaft 112. Thesubstrate 634 has one or more position detection sensors 636A, 636Bmounted thereon. As shown in FIG. 6 e , position detection sensors 636A,636B can be mounted to one of a surface facing the front-end 114 orsurface facing the rear-end 116 of the substrate 634. Based on theposition detection sensors 636A, 636B, the position of the motor shaftcan be detected based on the rotation of the code disks 632A, 632Bmounted to the motor shaft 110 and actuator shaft 112. As shown in FIG.6 f , the position detection sensors 636A, 636B can be mounted on bothsides of the single substrate, which result in increased accuracy andredundancy in detecting the motor position based on the rotation of codedisks 632A, 632B.

FIG. 6 g illustrates an exemplary encoder assembly having a singlesubstrate with a radial off-axis encoder and an on-axis encoder inaccordance with an exemplary embodiment of the present disclosure. Asshown in FIG. 6 g , the encoder assembly 126 can include a substrate 634having a first portion 634A and a second portion 634B that extends in adirection perpendicular to the first portion 634A. The positiondetection sensor 636B can be mounted on the first substrate portion 634Ato be in on-axis alignment with a code disk 632B mounted in the hollowvolume of the actuator output shaft 112. A position detection sensor636C can be mounted on the second substrate portion 634B to be inoff-axis alignment with a code disk 632C mounted to an outer surface ofthe motor shaft 110. The position detection sensor 636C is aligned todetect signals from the pairs of N and S poles 525 arranged on a radialsurface 610 or outer edge of the code disk 632C.

The exemplary rotary encoder assemblies of the present disclosure aremounted on a single substrate, which allows for much smaller spacerequirements over known implementations. As a result, the encoderassemblies as described herein can be mounted closer to themotor/actuator allowing for a reduction in the length resulting inimproved torque density. As a result, when the encoder assembly, whichuses a dual encoder combination on a single substrate, is integrateddirectly on an integrated servo drive the encoder wires can beeliminated completely. In addition, the position detectors can beconnected in a daisy-chain configuration, which leads to space andthermal efficiencies, as well as a reduction of the number of wires tobe connected to the servo drive or controller. The encoder assemblyhaving components and circuitry mounted on both sides of a double-sidedsubstrate introduce not only space savings but cost savings as well. Tofurther improve performance of the encoder assembly, the motor/actuatorshaft can be formed of aluminum to reduce the amount of crosstalk andnoise from magnetic interference, improve torque density, and reduceinertia or eliminate shaft runout. The use of other known mountingtechniques and materials with respect to the magnets can be used toimprove tolerances, electrical runout, and overall performance of theencoder assembly.

It will thus be appreciated by those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. The presently disclosedembodiments are therefore considered in all respects to be illustrativeand not restricted. The scope of the invention is indicated by theappended claims rather than the foregoing description and all changesthat come within the meaning and range and equivalence thereof areintended to be embraced therein.

What is claimed is:
 1. An encoder assembly, comprising: a first codecomponent mounted to a first rotating shaft; a second code componentmounted to a second shaft; one or more substrates; a first positiondetection sensor mounted to a surface of the one or more substrates inan on-axis or off-axis alignment with the first rotating shaft, thefirst position detection sensor detecting signals from the first codedisk mounted to the first rotating shaft; and a second positiondetection sensor mounted to the surface of the one or more substrates inan on-axis or an off-axis alignment with the second shaft, the secondposition detection sensor detecting signals from the second code diskmounted to the second shaft.
 2. The encoder assembly according to claim1, wherein: the one or more substrates includes a first substratemounted in parallel with the axis of the first rotating shaft and asecond substrate mounted orthogonally or in parallel with the axis ofthe second shaft, wherein the second substrate when mounted in parallelwith the axis of the second shaft is connected to the first substrate,and the first code component includes a first code disk and the codecomponent includes a second code disk.
 3. The encoder assembly accordingto claim 2, wherein the first rotating shaft and the second shaft arecoaxial.
 4. The encoder assembly according to claim 2, wherein the firstposition detection sensor detects signals from a radial surface of thefirst code disk.
 5. The encoder assembly according to claim 2, whereinthe first rotating shaft is a motor shaft and the second shaft is anactuator output shaft.
 6. The encoder assembly according to claim 2,wherein the first rotating shaft and the second shaft are motor shafts.7. The encoder assembly according to claim 1, wherein the first rotatingshaft and the second shaft are motor shafts.
 8. The encoder assemblyaccording to claim 1, wherein the first and second position detectionsensors in combination with the first and second code disks,respectively, form dual single-turn absolute encoders.
 9. The encoderassembly according to claim 1, wherein the first and second positiondetection sensors in combination with the first and second code disks,respectively form dual multi-turn absolute encoders.
 10. The encoderassembly according to claim 1, further comprising: at least oneredundant position detection sensor mounted to the one or moresubstrates, wherein the at least one redundant position detection sensoris mounted relative to at least one of the first and the second positiondetection sensors on a surface of the one or more substrates.
 11. Theencoder assembly according to claim 2, further comprising: at least oneredundant position detection sensor mounted to each of the firstsubstrate and the second substrate, wherein the at least one redundantposition detection sensor is mounted relative to at least one of thefirst and the second position detection sensors on a respective radialsurface of the substrate.
 12. The encoder assembly according to claim 1,wherein the one or more substrates are flexible.
 13. The encoderassembly according to claim 2, wherein the first substrate is mountedradially from an axis of the first rotating shaft.
 14. The encoderassembly according to claim 1, wherein the first or second positiondetection sensors are mounted on a radial surface of the one moresubstrates.
 15. The encoder assembly according to claim 2, wherein thefirst or second position detection sensors are mounted on an axialsurface of the one more substrates.
 16. The encoder assembly accordingto claim 14, wherein the first position detection sensor and the secondposition detection sensor are mounted on opposite sides of the one ormore substrates.
 17. The encoder assembly according to claim 14, furthercomprising: at least one redundant position detection sensor, whereinthe at least one redundant position detection sensor is mounted relativeto at least one of the first and the second position detection sensorson the radial surface of the one or more substrates.